#include <iostream>

using namespace std;

//命名空间在全局范围定义
//命名空间可以嵌套定义
namespace a{
    extern int x,y;
    int fun(int arg);
    int square(int a);
    namespace b{
    int fun(int a);
    }
}
namespace b{
    extern int x,y;
    int fun(int arg);
    int square(int b);
}


int main()
{
    //using namespace a;

   // cout << "Hello World!" << endl;
    //cout<<"fun"<<a::b::fun(10)<<endl;
    //cout<<"square"<<b::square(10)<<endl;
    char *p=new(char);
    if(*p!=NULL)
    {
        cin>>p;
        cout<<"p:"<<*p<<endl;
    }
    else {
       cout<<"NULL"<<endl;
    }

    char *data=new char[10];
    if(*data!=NULL)
    {
        cin>>data;
        cout<<"data :"<<data<<endl;
    }
    else {
        cout<<"NULL"<<endl;
    }
    delete [] data;
    return 0;
}
